For Cognos 8.3, there is no need to modify the QSRVUITextRL_en.xml as noted for earlier version of Cognos 8. Instead locate and edit the viewer_XX.properties file (where XX stands for the locale you use such as EN for example) under c8\webapps\p2pd\WEB-INF\classes. Ensure to backup this file prior to making any modification.
Edit the file by finding the following 3 lines:
RV_BUSY_OPTIONS_SELECTED = Instead of waiting, you can set it to run in the background with one of the following delivery options: RV_BUSY_OPTIONS_UNSELECTED = Instead of waiting, you can select a delivery method to run the report in the background. RV_BUSY_OPTIONS_LINK = Select a delivery method.